Nanoparticle Systems — PLGA, SLN, and NLC

Polymeric nanoparticles fabricated from poly(lactic-co-glycolic acid), universally abbreviated PLGA, represent one of the most extensively studied...

Polymeric nanoparticles fabricated from poly(lactic-co-glycolic acid), universally abbreviated PLGA, represent one of the most extensively studied nanocarrier platforms, owing to the polymer's biodegradability, biocompatibility, and long history of regulatory acceptance in approved products. PLGA nanoparticles are commonly prepared by nanoprecipitation, in which drug and polymer dissolved in a water-miscible organic solvent such as acetone are introduced dropwise into an aqueous phase containing a stabiliser such as polyvinyl alcohol, causing spontaneous nanoparticle formation as the solvent diffuses into the aqueous phase; by double emulsion methods, particularly suited to hydrophilic drugs, in which a primary water-in-oil emulsion is further emulsified into an outer aqueous phase; or by emulsification-solvent diffusion techniques employing partially water-miscible solvents. Key process variables governing the resulting particle characteristics include the molecular weight of the PLGA employed, generally in the range of ten to one hundred kilodaltons, the drug-to-polymer ratio, the choice and concentration of stabiliser, and the energy input during emulsification.

Solid Lipid Nanoparticles, abbreviated SLN, and Nanostructured Lipid Carriers, abbreviated NLC, constitute a related lipid-based nanocarrier family that offers particular advantages of biocompatibility and scalable manufacture, since their lipid matrices are generally regarded as safe and their production avoids the use of potentially toxic organic solvents required for many polymeric systems. SLN comprise a solid lipid core stabilised by surfactant, while NLC incorporate a blend of solid and liquid lipids, producing a less ordered crystalline matrix that affords higher drug loading capacity and reduces the risk of drug expulsion during storage that can affect purely solid lipid matrices as they undergo polymorphic transition toward a more ordered, lower-capacity crystal form.

These nanoparticulate systems find their principal pharmaceutical application in addressing the poor oral bioavailability characteristic of BCS Class II and IV drugs, in enabling parenteral depot formulations that provide sustained systemic release, and, through appropriate surface modification, in achieving passive or active targeting to specific tissues such as tumours, exploiting the enhanced permeability and retention effect characteristic of many solid malignancies. Industrially, nanoparticle manufacture presents distinct scale-up challenges relative to conventional dosage forms, particularly around maintaining consistent particle size and encapsulation efficiency as batch volumes increase, and continuous manufacturing approaches employing microfluidic or impinging-jet mixing technology are increasingly adopted to address this challenge.